Jaysh al-Islam is a Sunni Muslim group that is part of a new, Saudi-backed opposition body set up with the aim of bringing about peace talks between rebels and the Iranian-backed Syrian government led by President Bashar al-Assad.

The group, whose leader was killed in a Dec 26 air strike, said Iran was “threatening the security of the region by exporting criminal militias that spread destruction and death and filled with sectarian vengeance”.

The European Union’s foreign policy chief warned Iran’s foreign minister on Sunday that renewed tension between Shia Iran and Saudi Arabia’s Sunni monarchy could wreck efforts to find a political solution for the crisis in Syria.

Saudi Arabia condemned the killing of Jaysh al Islam’s leader Zahran Allosuh in an aerial raid in his stronghold east of Damascus, saying his death did not serve the peace process in the war-torn country.

Iranian-backed militias and Lebanese Shia militant group Hezbollah are fighting alongside the Syrian army against mainly Sunni insurgents backed by Saudi Arabia, other Gulf states and Turkey in a conflict that has cost over 250,000 lives.